#if !defined MOVEPICK_H_INCLUDED
#define MOVEPICK_H_INCLUDED


////
//// Includes
////














#include <array>
#include <limits>
#include <type_traits>

#include "movegen.h"
#include "position.h"
#include "types.h"



/// StatsEntry stores the stat table value. It is usually a number but could
/// be a move or even a nested history. We use a class instead of naked value
/// to directly call history update operator<<() on the entry so to use stats
/// tables at caller sites as simple multi-dim arrays.
template<typename T, int D>
class StatsEntry {

	static const bool IsInt = std::is_integral<T>::value;
	typedef typename std::conditional<IsInt, int, T>::type TT;

	T entry;

public:
	T * get() { return &entry; }
	void operator=(const T& v) { entry = v; }
	operator TT() const { return entry; }

	void operator<<(int bonus) {
		assert(abs(bonus) <= D);   // Ensure range is [-D, D]
		static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");

		entry += bonus - entry * abs(bonus) / D;

		assert(abs(entry) <= D);
	}
};

/// Stats is a generic N-dimensional array used to store various statistics.
/// The first template parameter T is the base type of the array, the second
/// template parameter D limits the range of updates in [-D, D] when we update
/// values with the << operator, while the last parameters (Size and Sizes)
/// encode the dimensions of the array.
template <typename T, int D, int Size, int... Sizes>
struct Stats : public std::array<Stats<T, D, Sizes...>, Size>
{
	T* get() { return this->at(0).get(); }

	void fill(const T& v) {
		T* p = get();
		std::fill(p, p + sizeof(*this) / sizeof(*p), v);
	}
};

template <typename T, int D, int Size>
struct Stats<T, D, Size> : public std::array<StatsEntry<T, D>, Size> {
	T* get() { return this->at(0).get(); }
};

/// In stats table, D=0 means that the template parameter is not used
enum StatsParams { NOT_USED = 0 };

/// ButterflyHistory records how often quiet moves have been successful or
/// unsuccessful during the current search, and is used for reduction and move
/// ordering decisions. It uses 2 tables (one for each color) indexed by
/// the move's from and to squares, see chessprogramming.wikispaces.com/Butterfly+Boards
typedef Stats<int16_t, 10368, COLOR_NB, int(90) * int(256)> ButterflyHistory;

/// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
/// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
typedef Stats<Move, NOT_USED, 16, 90> CounterMoveHistory;

/// CapturePieceToHistory is addressed by a move's [piece][to][captured piece type]
typedef Stats<int16_t, 10368, PIECE_NB, 90, 8> CapturePieceToHistory;

/// PieceToHistory is like ButterflyHistory but is addressed by a move's [piece][to]
typedef Stats<int16_t, 29952, PIECE_NB, 90> PieceToHistory;

/// ContinuationHistory is the combined history of a given pair of moves, usually
/// the current one given a previous one. The nested history table is based on
/// PieceToHistory instead of ButterflyBoards.
typedef Stats<PieceToHistory, NOT_USED, PIECE_NB, 90> ContinuationHistory;


/// MovePicker class is used to pick one pseudo legal move at a time from the
/// current position. The most important method is next_move(), which returns a
/// new pseudo legal move each time it is called, until there are no moves left,
/// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
/// beta algorithm, MovePicker attempts to return the moves which are most likely
/// to get a cut-off first.
class MovePicker {

	enum PickType { Next, Best };

public:
	MovePicker(const MovePicker&) = delete;
	MovePicker& operator=(const MovePicker&) = delete;
	MovePicker(const Position&, Move, Value, const CapturePieceToHistory*);
	MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
		const CapturePieceToHistory*,
		Square);
	MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
		const CapturePieceToHistory*,
		const PieceToHistory**,
		Move,
		Move*);
	Move next_move(bool skipQuiets = false);

private:
	template<PickType T, typename Pred> Move select(Pred);
	template<GenType> void score();
	ExtMove* begin() { return cur; }
	ExtMove* end() { return endMoves; }

	const Position& pos;
	const ButterflyHistory* mainHistory;
	const CapturePieceToHistory* captureHistory;
	const PieceToHistory** contHistory;
	Move ttMove;
	ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
	int stage;
	Move move;
	Square recaptureSquare;
	Value threshold;
	Depth depth;
	ExtMove moves[MAX_MOVES];
};

#endif // !defined(MOVEPICK_H_INCLUDED)
